1. Field of the Invention
The present invention relates generally to wet-dye, hard copy apparatus, more particularly to staggered pen arrangement in ink-jet printers, and more specifically to a method of improved throughput printing, including simultaneous printing on multiple pages.
2. Description of Related Art
The art of wet-dye printingxe2x80x94such as with ink-jet technology, liquid toner laser technology, and the likexe2x80x94is relatively well developed. For example, commercial ink-jet products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of ink-jet technology are disclosed, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 ( May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1 (February 1994) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13, (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
In U.S. Pat. No. 5,376,958 (assigned to the common assignee of the present invention and incorporated herein by reference) for Staggered Pens in Color Thermal Ink-Jet Printer to Brent Richtsmeier, et al. (hereinafter xe2x80x9cRichtsmeierxe2x80x9d), a color ink-jet printer includes a print carriage movable along a carriage scan axis and a plurality of color producing ink-jet printheads supported by the print carriage and offset relative to each other so that their nozzle arrays are non-overlapping along the media scan axis (perpendicular to the carriage scan axis). The nozzle arrays of the ink-jet printheads traverse non-overlapping regions as the carriage is scanned along the carriage scan axis. The construct thus provides for drying of ink drops prior to application of any overlying ink drops.
Generally, the pen scanning axis is referred to as the x-axis, the print media transport axis is referred to as the y-axis, and the ink drip firing direction is referred to as the z-axis. See e.g., FIGS. 1-3.
It is a perennial goal of hard copy apparatus designers to increase throughput, an important consideration for the end-user. Thus, among hard copy apparatus original equipment manufacturers, the design criteria is xe2x80x9cfaster is better.xe2x80x9d For scanning carriage ink-jet technology, the goal is to try to match the substantially faster page-per-minute (xe2x80x9cppmxe2x80x9d) capability in state-of-the-art electrostatic and laser printing technology.
In thermal ink-jet technology, the use of thin-film and semiconductor technology to produce printheads has permitted the nozzle density to increase. In other words, where only a few years ago Hewlett-Packard(trademark) DeskJet(trademark) Stanley-model printheads had a nozzle array height of about one-sixth inch with nozzles separated by {fraction (1/180)}th-inch, the state of the art has progressed to where nozzle arrays of one or more inches in height with hundreds of nozzles separated by only {fraction (1/600)}th-inch. It can thus be recognized that in a standard ink-jet scanning printer, throughput efficiency is degraded with the larger printheads because many nozzles will not be firing as swaths are created along leading and trailing edges of the print media, namely, when part of the printhead is hanging over the edge of the page.
In its basic aspects, the present invention provides a method for ink-jet printing, including the steps of: transporting sheets of print media sequentially in a first direction through an ink-jet printing zone such that a leading edge of a print media sheet is substantially adjacent to a trailing edge of a sequentially preceding print media sheet; aligning a set of ink-jet printheads in series in a plane adjacent to the printing zone and parallel to the first direction; and printing a first swath in a second direction perpendicular to the first direction with one of the ink-jet printheads of the set on or adjacent to the leading edge while simultaneous printing a second swath with another one of the ink-jet printheads of the set on or adjacent to the trailing edge.
In another basic aspect, the present invention provides an ink-jet hard copy apparatus, including: carriage mechanisms for moving along a carriage scan axis; transport mechanisms for transporting print media sequentially through a printing zone along a media transport axis that is substantially orthogonal to the carriage scan axis; and a plurality of ink-jet printheads supported by the carriage mechanisms in sequential locations along the media transport axis, each of the printheads having at least one nozzle array having a height in the media transport axis, and the printheads are offset in the media transport axis relative to each other by approximately a distance less than or equal to the height when the pens have the same color ink and equal to or greater than the height when the pens have different color ink.
In another basic aspect, the present invention provides a color ink-jet hard copy apparatus, having: a printing zone; a paper feed device mounted for transporting paper sheets sequentially through the printing zone along a predetermined paper path, sequentially transported sheets having a respective trailing edge leading edge first gap along the paper path; a scanning carriage mounted with respect to the paper path adjacent to the printing zone for moving along a scan axis that is substantially orthogonal to the paper path; and a set of ink-jet writing instruments mounted to the carriage for depositing droplets of ink on paper sheets transported adjacently thereto by the paper feed device, each of the writing instruments including at least one ink-jet printhead, each printhead including at least one nozzle array having a predetermined array height in a direction along the paper path, the set further having at least two black ink writing instruments mounted to the carriage in series along the paper path such that the respective printheads of the black ink writing instruments are separated from each other by second gap having a distance of at least approximately the predetermined array height, and at least two color ink writing instruments mounted to the carriage in series along the paper path such that the respective printheads of the black ink writing instruments are separated from each other by a distance of at least approximately the predetermined array height and staggered from the black ink writing instruments in the scan axis such that one of the color ink writing instruments is mounted adjacent to the second gap.
It is an advantage of the present invention that it provides for simultaneous multi-page printing.
It is an advantage of the present invention that it provides significantly increased throughput capability for ink-jet hard copy apparatus.
It is an advantage of the present invention that it maximizes printing speed in scanning printhead, single pass, printing.
It is an advantage of the present invention that it can be scaled as printhead size increases.
It is another advantage of the present invention that hard copy apparatus throughput advantages increase as the print swath size increases.
Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings.